The present invention relates to device for injecting, infusing, delivering, administering or dispensing a substance, and to methods of making and using such devices. More particularly, it relates to the field of injection devices, including automatic injection devices or autoinjectors, for administering a liquid product, e.g. a medicinal or therapeutic substance or product or a medicament.
U.S. Pat. No. 3,797,489 discloses an injection device comprising a driving spring acting on a product container or a plunger of the product container and a spring opposing the driving spring via the product container. The opposing spring has three functions, that of acting as a damper, a safety mechanism and a moving the needle back by a short amount. The driving spring is coupled with the opposing spring during both the injection process via a fixed coupling with the product container and during the dispensing movement via the liquid of the product container. In the case of this device, the task of balancing the spring forces represents a major challenge.
EP 0 516 473 B1, EP 1 503 816 B1 and U.S. Pat. No. 6,387,078 each disclose injection devices in which the driving spring is uncoupled from the return spring after the product has been dispensed, i.e. after the dispensing movement has ended to retract the injection needle.